Internal-combustion heater with knipp&#39;s singing tubes



DEN M COLLUM INTERNAL-COMBUSTION HEATER WITH KNIPPS SINGING TUBES May31, 1949.

2 Sheets-Sheet 1 Filed March 23, 1945 H. J. DE N. MGCOLLUMINTERNAL-COMBUSTION HEATER WITH May 31, 1949.

KNIPPS SINGING TUBES 2 Sheets-Sheet 2 Filed March 23, 1945 Am? uvzzrHEAT APPLIED MERE Patented May 31, 1949 UNITED STATES PATENT OFFICEINTERNAL-COMBUSTION mm mm xmr-r's smomo mas Henry J. De N. McOollum,deceased, 1m cago,.lll., by Thelma McOollum, exeoptrix, Ohicago, 11].,assignor to Stewart-Warner Corporation, (lhicago, Ill., a corporation ofVirginia Application March 23, 1945, Serial No. 584,361

Claims. (Cl. 126-118) The invention relates generally to heaters, andmore particularly to heaters of the sealed combustion type and to meansfor inducing flow of combustion and ventilating air through suchheaters.

It has been known for some time, as a scientiflc curiosity, that arelatively long tube having a bulbous enlargement at one endin which islocated an open end tube with its open end facing the closed end of thebulb, will, if the bulbous portion is heated, emit a musical tone. Thisapparatus is generally known as a Knipps singing tube.

The fundamental principle of the invention is based upon the discoverythat flow of air may readily be induced by such singing tubes, and thetubes thus used in the place of fans or blowers to circulate air. Thisprinciple is illustrated herein as applied to sealed combustion typeheaters for producing the flow of ventilating air and air forcombustion. 4

It is thus an object of the invention to provide an improved sealedcombustion type heater in which the flow of ventilating air and the flowof air for combustion is induced by singing tubes heated by the heater.

A further object is to provide an improved simplifled apparatus forconverting energy in the form of heat to the kinetic energy of flowingases.

A further object is to provide an improved heater of the sealedcombustion type, which does not require the use of a blower, fan, orother power-operated means to cause the flow of ventilating air throughthe heater.

Other objects will appear from the following description, referencebeing had to the accompanying drawings, in which:

Fig. l is a central longitudinal sectional view of a heaterincorporating the invention;

Fig. 2 is a similar view of a modified form of the invention:

Fig. 3 is a diagrammatic sectional view of a further embodiment of theinvention; and

Fig. 4 is a, central longitudinal sectional view secured thereto toincrease the rate at which heat may be dissipated therefrom.

A plurality of singing tubes 22 are secured to the wall I4 as bywelding. Each singing tube has an enlarged diameter bulb-shaped portion24, the extremity 26 of which projects through a suitable opening formedin the conical wall l4. Within the bulbous portion 24 of each of thetubes there is located a smaller diameter tube 28 having an open endadjacent the portion 28 of the bulb, and having its other end closed.The tube 28 is suitably spaced from the walls of the bulb portion 24 bymeans of spiders 30. The open end of one of the singing tubes 22 isclosely adjacent the open end of a larger diameter combustion air supplytube 32 which leads into the combustion chamber l2, extending inwardlytherein in an arcuate direction so as to impart swirling motion to theair in the combustion chamber.

A two-position valve 34 is provided, this valve normally closing theoutlet opening of a hand operated blower 38 and moving to its dottedline position when the blower is being operated. Fuel is supplied to thecombustion chamber from a suitable source under pressure through aconduit 38, a suitable fuel metering device 40 being. provided to causethe fuel to flow into the combustion chamber in a regulated amount andin atomized form. An electrical igniter 42 is suitably secured inchamber which communicates with the combustion chamber through ports 44.

To cause operation of the heater, the fuel supply is turned on, theelectrical igniter is energized, and the blower 36 is operated tointroduce combustion air to the combustion chamber. After hand operationin this manner for a suflicient length of time, the bulbs 26 will becomeheated sufliciently to cause the tubes to sing, that is, to cause highamplitude oscillations of the air within the tubes. The frequency ofsuch oscillations is determined by the dimensions of the tube. For bestresults, the singing tube should be designed to oscillate at frequenciesof the order of 200 to 600 C. P. S.

ment with the opening of the combustion air supply tube 32 causes air tobe iorced into the latter tube. Apparently the alternate pulsations oithe air at the end of the tube 22 imparts sufficient kinetic energy tothe air to cause it to enter the tube 32 upon the pressure portion ofcauses the pulsations, whereas upon the rarefaction portion of thepulsating cycle. air is drawn from the space surrounding the ends of thetubes 22 and 32. The result is that a substantial quantity of air willenter the tube 32 at sumcient pressure to cause it to flow through thistube and into the combustion chamber of the heater.

To assist the singing tube in producing such flow of air, the exhaustconduit 20 is preferably discharged into a low pressure area along theskin of the airplane (If the heater is utilized for heating anairplane), or discharged into a stack in which natural convection willassist the singing tubes in producing such air flow. The singing tubes22, other than the one which is in alignment with the end of thecombustion air tube 32, produce flow oi ventilating air through thehousing lb. The flowing ventilating air picks up heat from the shell isand from fins which may be secured thereto, as well as from thecombustion chamber walls. In flowing past the portions of the singingtube other than the end 26. the ventilating air will cool such portionsand thus maintain the temperature differential required to cause thesinging tubes to continue to oscillate. Except for the initial use ofthe blower 36 to start the heater, it operates without any moving parts.

It will be understood that the heater will be provided with the usualtemperature responsive controls for cutting on the supply of current tothe igniter after combustion has been established. The heater is ineffect self-regulating, in that if the normally cooler portions oi thesinging tubes become excessively heated. the amplitude of airoscillation within them will decrease and hence less air for combustionwill be supplied. to the combustion chamber, thus causing a reduction inthe heat output. with the result that the normally cooler portions ofthe singing tubes will be cooled sumciently to induce oscillations ofnormal amplitude.

In Fig 2 there is illustrated a modified form of the invention, in whichthe singing tubes have only the ends of their bulbous portions suppliedwith heat. In this construction a short cylin clrical sheet metal boxso, which may be formed by welding the sheets together, is locatedwithin a housing as with sumcient clearance to permit the flow ofventilating air between the box as and the housing 66. An ignlter wellso is welded or otherwise suitably secured to the forward wall of thebox to and contains a suitable ignlter 50, preferably of theelectrically heated resistance wire type. The igniter well communicateswith the combustion chamber 52, formed within the box as, through aplurality of ports 54, 55. Fuel is supplied through a pipe I50 whichprojects into the combustion chamber 02 and may have a nozzle tipsecured thereto tocause partial atomization of the fuel.

The products of combustion are withdrawn from the combustion chamber 52through. an exhaust conduit 60 which projects a substantial distanceinto the combustion chamber so as to cause the burning fuel and productsof combustion to follow a circuitous path within the combustion chamber.

A plurality of singing tubes are arranged in a circle, being suitablyspaced from one another, and have the ends 60 of their enlarged diameterportions 68 projecting into the combustion chamber 52. In Fig. 2 onlytwo of the singing tubes are illustrated, but it will be understood thatany desired number may be suitably spaced, preferably in a circularpattern, within the dimensional limits or the combustion chamber 02.

Within each of the enlarged portions 66 of the singing tubes there Islocated the open end, small diameter tube 88 supported so as to lieco-axially with the portions 00 by a pair of spiders Ill. The outlet endof one of the tubes 82 is spaced a short distance from the and I2 of acombustion air supply tube It, the latter extending inwardly to thecombustion chamber in a generally tangential direction so as to impart aswirling rotary motion to the mixture in the combustion chamber.

A shell E6 of generally cylindrical contour, is supported within thehousing 36, so as to be ccaxial therewith, by a plurality of bracketsIt. The shell it has an end wall 00, provided with a plurality of flaredopenings s2, one surrounding each of the ends of the singing tubes 62.

The singing tubes 62 operate in the manner described with reference toFig. 1 to cause the ilow of combustion air into the combustion chamberand to cause now or ventilating air through the openings 82 in the endwall of the shell it. The air flowing from these openings will induceflow of air through the annular space between the shell 16 and housingas. The ventilating air will maintain the portions of the singing tubes62, other than their end portions 65, sufficiently cooler than theportions so to maintain oscillation.

To cause the heater to commence operation a supply of air underpressure, or a hand-operated blower, is connected to a T as to supplythe initial air for combustion. The air pressure from such auxiliarysupply will swing a spring-returned flap valve 98 to its dotted lineposition and thus permit flow of air into the combustion chamber. Afterthe heater has commenced normal operation, the auxiliary air supply maybe disconnected from the T as, whereupon the valve to will be springreturned to its full line position and combustion air will be suppliedthrough the tube 74 by virtue of the flow induced by its associatedsinging tube 62.

Since the oscillations produced by the singing tubes are usually wellwithin the audible range and normally of high amplitude, and since theymay not be of exactly the same frequency, it is usually desirable toprovide means for mufliing or suppressing the sounds produced. In Fig. 3there is diagrammatically illustrated a suitable means for mutliing thesound produced. This means may be incorporated in either of the heatersshown in Figs. 1 or 2, or in the heater shown in Fig. 4, subsequently tobe described.

In the apparatus shown in Fig. 3 the singing tube 90 has a reduceddiameter portion 92 and a bulbous portion 94, the extremity 96 of whichis adapted to be heated. Within the bulbous portion 94, is located thetube 98, having an open end directed toward the extremity 96 of thebulbous portion. The tube 98 is held co-axially in the bulbous portion94 by any suitable means, such as projecting lugs I00. The open end ofthe smaller diameter portion 92 of the singing tube is further reducedin diameter, as indicated at I02, and this end projects into an elbow I04. The elbow I04 has a perforated air inlet tube I06 which issurrounded by a casing I08, the space between this casing and the tubeI06 being preferably filled with a suitable sound absorptive and dampinmaterial IIO, such as rock wool, stainless steel wool, or glass wool. Anair outlet tube II2, forming part of the elbow I04, is likewiseperforated. surrounded by a casing Ill, with the space between theseelements filled with one of the named sound damping materials H0. Theair outlet tube H2 is co-axial with the singing tube 02 so that thepulsations produced in the latter will cause flow of air from the tube Ithrough the elbow I04 and into the outlet tube H2. The perforated tubesI06 and H2 operate as mumers to reduce the intensity of the soundtransmitted to the space surrounding these tubes. Since the singing tubeof given dimensions will always operate at substantially the samefrequency, the number and size of the perforations in the tubes I00,II2, as well as the dimensions of the casings I00, II4, may be made suchas to be most effective in damping the particular frequency which isgenerated.

In the form of the invention shown in Fig. 4 the heater comprises ahousing I surrounding a 'irusto-conical combustion chamber wall I22,which may be welded to an end wall I24, and a generally cylindricalshell I26 welded to the wall I22. Suitably secured to the end wall I24is an igniter well I20 havin an igniter I30 secured therein. The igniterI30 is preferably of the hot resistance wire type. The fuel and airmixture may flow into and out of the igniter well through suitableopenings I32 and I34. The products of combustion are exhausted from theshell I20 through a Venturi tube I36 having a throat portion I30. TheVenturi tube I may be formed as part of an exhaust conduit I40 whichpreferably discharges into a space of sub-atmospheric pressure.

, A singing tube I42 is mounted in the heater so as to have its bulbousend I44 projecting into the combustion chamber. Within the bulbousportion of the singing tube there is located the customary tube I46having an open end directed toward the closed end of the bulb. Anelectrical heating element I40 is wound around the bulbous portion ofthe singing tube for initially heating this portion. The heating elementI48 is shown as connected in series with the igniter I30, and in serieswith a thermostatic igniter switch I50, a manually operable controlswitch I52, and a suitable source of electrical energy, illustrated as abattery I54.

The outlet end I56 of the singing tube projects Into the Venturi tubeI35 so as to be positioned in reasonably close proximity .to the throatportion I30 thereof.

The form of the invention shown in Fig. 4 is 1 used whenever a suitablesource of ventilating air 1 under pressure is available. Under theseconditions it is not necessary to supply singing tubes for propellingthe ventilating air stream. In installations of this character asuitable fuel mixture from a carbureting means I50 is supplied to thecombustion chamber through a tube I02, the outlet end of which ispreferably directed tangentially of the combustion chamber.

In operating the heater shown in Fig. 4 the switch I52 is closed, eithermanually or under the control of a room thermostat, thus completing acircuit through the igniter, the heating element I40, and thethermostatic igniter switch I50. As the bulbous portion of the singingtube I42 becomes heated, the air therein will commence oscillation and,in cooperation with the Venturi tube I36, cause the flow of the productsof combustion outwardly through the exhaust pipe I40. The resultantreduction in pressure within the shell I20 and combustion chamber I22will cause flow of a fuel mixture from the carbureting means I00 to thecombustion chamber where it will be ignited by the Igniter I30. After ashort interval of operation, the bulbous end portion I44 of the singingtube will be heated by the flame in the combustion chamber and thethermostatic igniter switch will open to deenergize both the heatingelement I40 and the igniter I30. Thereafter the heater will continue inoperation, since the bulbous end portion I44 of the singing tube iscontinuously heated by the combustion flame, while the remaining portionthereof will be held at a lower temperature by the ventilating airflowing past it. In the event that the heater should become extinguishedaccidentally, the temperature of the ventilating air flowing past thethermostatic igniter switch I50 will drop and the latter switch willclose to reenergize the igniter I30 and the heating element I48,whereupon reignition will take place after a short interval.

As used in this specification and in the claims the term Knipps singingtube defines a structure comprising a relatively long tube having aclosed bulbous enlargement at one end thereof and, within the bulbousend portion and spaced from the walls thereof, a short closed end tubehaving its open end directed toward the closed end of the bulbous tube,the structure being such that when heat is applied to the bulbous end ofthe tube whil the remainder of the tube is at a lower temperature,acoustic vibrations occur in the tube. In these tubes the wave length ofthe acoustic vibrations is four times the sum of the length of, thebulbous tube and the length of the short closed end tube which isenclosed in the bulbous portion of the longer tube.

It will be apparent to those skilled in the art that while a number ofmodifications of the invention are disclosed herein, many additionalmodifications of the invention may be made without departing from theunderlying principles of the invention. It is therefore intended by thefollowing claims to include within the scope of the invention all suchmodifications and variations by which substantially the results of theinvention may be obtained by the use of substantially the same orequivalent means.

Th invention claimed is:

1. Means for causing the flow of air, comprising a pipe having an openend, an elongated tube having a bulb at one end and being open at theother end, said latter end being closely adjacent the open end of thepipe and in substantial alignment therewith, a tubular element enclosedwithin the bulbous end of said tube, said tubular element being open atthe end facing the end of said tube and closed at its opposite end,means for supporting said element co-axially with respect to saidbulbous end portion, and means for heating th bulbous end portion ofsaid tube.

2. In a sealed combustion type heater having means forming a combustionchamber, means for supplying fuel to said combustion chamber, and meansfor igniting the fuel mixture in the combustion chamber, and means forcausing flow of air for combustion and flow of ventilating air to beheated including passage forming means and a plurality of Knipps singingtubes having their closed bulbous ends projecting into said combustionchamber, said singing tubes having their open ends communicating withsaid passages in a direction to induce the fiow of air through saidpassages.

3. The combination set forth in claim '2 in which there is providedmeans including a manually operated blower for supplying combustion airduring the starting period while the singing tubes are ineffective tocause air flow.

4. In an apparatus for causing the flow of a gaseous fluid, thecombination of a Knipp's singing tube having an open end, a pipe havingan open end adjacent to, but spaced from, the open end of said singingtube and in substantially axial alignment therewith, and means forsupplying heat to the closed end portion only of the singing tube.

5. The combination set forth in claim 4, in which said pipe has aVenturi tube form at the open end thereof which is located adjacent tothe open end of the singing tube.

6. The combination set forth in claim 4, in which said pipe is providedwith a plurality of relatively small perforations, in which theperforated portion of said pipe is surrounded by a casing, and in whichthe space between said pipe and casing is packed with a heat resistant,sound damping material.

7. In a heater having means forming a combustion chamber, a heatexchanger communicating therewith and a ventilating air duct structureto convey air to be heated past said heat exchanger, and having meansfor supplying a combustible mixture to the combustion chamber andigniting it, the combination of a Knipp's singing tube having its closedbulbous end portion projecting into the combustion chamber and having asecond portion located in the flow path of ventilating air, an exhaustconduit connected to the heat exchanger to provide a passageway for thedischarge of the products of combustion from the heat exchanger, theopen end of said singing tube projecting into said exhaust conduit inalignment with a portion thereof-to induce flow of the products ofcombustion from the heat exchanger through said exhaust conduit, and anelectrical heating element for heating the bulbous portion of saidsinging tube during starting of the heater.

8. In a heater of the sealed combustion type, including means forming acombustion chamber, a heat exchanger and a ventilating air ductstructure to convey air to be heated past said heat exchanger, aplurality 'of singing tubes, each having its closed end in closeproximity to said combustion chamber forming means so as to be heated bythe burning gases within the combustion chamber, means for supplying airfor combustion to said combustion chamber, said means comprising a pipehaving an open end in substantial alignment with and closely adjacentthe open end of one of said singing tubes, means for supplying fuel tothe combustion chamber and igniting the combustible mixture therein, the

8 open end or the other singing tubes being in the ventilating airstream and in a direction to propel the ventilating air to a space to beheated.

9. Apparatus for causing the flow of a gas, comprising a Knipps singingtube having a bulbous end portion and a tubular element within thebulbous end portion, the tubular element having an open end facing theclosed end of the bulbous end portion and being closed at its oppositeend, means for applying heat to the bulbous end portion to raise itstemperature above that of the remaining portion of the singing tube, andan air propulsion pipe having its end in substantial alignment with theopen end of the singing tube and spaced therefrom a sutllcient distanceto cause the vibratory oscillations of the air in the singing tube toinject air into the pipe with substantial kinetic energy.

10. In a sealed combustion type heater having means forming a combustionchamber, a heat exchanger communicating therewith, a ventilating airduct structure to convey air to be heated past said heat exchanger,means for supplying fuel to the combustion chamber, and an igniter, thecombination of means for causing the flow of air for combustionincluding passage forming means and a Knipp's singing tube having itsclosed bulbous end portion projecting into the combustion chamber andhaving a second portion located in the now path of the ventilating air,said singing tube having its open end communicating with said passage ina direction to induce the now of air therethrough.

THZELMA MCCOLLUM. Executrir o! the Last Will and Testament of Henry J.De N. McCollum, Deceased.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 'Number Name Date 1,729,579 Hayes Sept. 24, 19292,204,226 Nelson June 11,1940 2,363,168 Findley Nov. 21, 1944 FOREIGNPATENTS Number Country Date 505,891 France May 17, 1920 OTHER.REFERENCES A Textbook of Sound," by A. B. Wood, 2nd edition, publishedby the Macmillan Company in

